EXHAUST SYSTEM FOR INTERNAL COMBUSTION ENGINE

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2024-198688 filed on Nov. 14, 2024. The disclosure of the above-identified application, including the specification, drawings, and claims, is incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to an exhaust system for an internal combustion engine.

2. Description of Related Art

An exhaust system is known in which a particulate filter is disposed in the middle of an exhaust pipe assembly for an internal combustion engine (see, for example, Japanese Unexamined Patent Application Publication No. 2007-085292 (JP 2007-085292 A), Japanese Unexamined Patent Application Publication No. 2022-098109 (JP 2022-098109 A), and Japanese Unexamined Patent Application Publication No. 2018-150928 (JP 2018-150928 A)). The exhaust system includes a differential pressure sensor for detecting a differential pressure between an exhaust pressure upstream of the particulate filter and an exhaust pressure downstream of the particulate filter.

SUMMARY

An object of the present disclosure is to provide a technique capable of restraining a pipe of a differential pressure sensor from being blocked due to freezing of condensed water.

An aspect of the present disclosure relates to an exhaust system for an internal combustion engine. In this case, an exhaust system for an internal combustion engine, for example, includes

• • a particulate filter disposed in a middle of an exhaust pipe assembly for the internal combustion engine,
  • an upstream side pipe connected to the exhaust pipe assembly upstream of the particulate filter,
  • a downstream side pipe connected to the exhaust pipe assembly downstream of the particulate filter, and
  • a differential pressure sensor connected to the upstream side pipe and the downstream side pipe and configured to detect a differential pressure between an exhaust pressure upstream of the particulate filter and an exhaust pressure downstream of the particulate filter,
  • in which the upstream side pipe and the downstream side pipe may be configured to exchange heat through a heat exchanger.

According to the present disclosure, it is possible to provide a technique capable of restraining the pipe of the differential pressure sensor from being blocked due to the freezing of the condensed water.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

FIG. 1 is a diagram schematically showing an example of a configuration of an exhaust system of an internal combustion engine in the embodiment;

FIG. 2 is a cross-sectional view schematically showing an example of a configuration of the first bracket in the embodiment; and

FIG. 3 is a cross-sectional view schematically showing an example of the configuration of the second bracket in the embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

As an exhaust system of an internal combustion engine (gasoline engine) that uses gasoline as fuel, an exhaust system including a gasoline particulate filter (GPF) in the middle of an exhaust pipe is known. In such an exhaust system, a differential pressure sensor may be provided to detect the removal of the GPF or the like. The differential pressure sensor is connected to an upstream side pipe connected to an exhaust pipe upstream of the GPF and a downstream side pipe connected to an exhaust pipe downstream of the GPF, and detects a differential pressure between an exhaust pressure upstream of the GPF and an exhaust pressure downstream of the GPF. By the way, the downstream side pipe extends to a position away from the internal combustion engine that is the heat source (a position downstream of the GPF) as compared with the upstream side pipe, and thus is easily affected by the outside air. Therefore, in an environment in which the outside air temperature is below freezing point, such as a cold region, the condensed water may freeze in the downstream side pipe. When the condensed water is frozen in the downstream side pipe, the passage in the downstream side pipe is blocked, and there is a possibility that the differential pressure sensor cannot detect an accurate differential pressure. Therefore, a measure for suppressing freezing of the condensed water in the downstream side pipe is requested.

Therefore, in the exhaust system for an internal combustion engine according to the present disclosure, the upstream side pipe and the downstream side pipe connected to the differential pressure sensor are configured to exchange heat through the heat exchanger. Here, since the connection portion between the upstream side pipe and the exhaust pipe is located near the internal combustion engine that is the heat source as compared with the connection portion between the downstream side pipe and the exhaust pipe, a relatively large amount of thermal energy is conducted from the exhaust pipe to the upstream side pipe. Therefore, the upstream side pipe has more thermal energy than the downstream side pipe. Then, the thermal energy of the upstream side pipe is conducted to the downstream side pipe through the heat exchanger. As a result, the temperature of the downstream side pipe can be increased. As a result, it is possible to suppress freezing of the condensed water in the downstream side pipe. Even in a case where the condensed water is frozen inside the downstream side pipe while the internal combustion engine is stopped, it is possible to quickly thaw the condensed water after the internal combustion engine is started.

The heat exchanger according to the present disclosure may be configured to position the upstream side pipe and the downstream side pipe such that the upstream side pipe and the downstream side pipe are disposed in parallel with each other along the flow direction of the exhaust gas. As a result, it is possible to shorten the length of the heat exchanger from the upstream side pipe to the downstream side pipe. Further, the length of the heat exchanger in the flow direction of the exhaust gas can be made longer, or the number of the places where the heat exchanger is provided can be increased. As a result, it is possible to increase the amount of thermal energy conducted from the upstream side pipe to the downstream side pipe.

The heat exchanger according to the present disclosure may be configured to include one or more brackets that connect the upstream side pipe and the downstream side pipe to each other in a state of being disposed close to each other in parallel. As a result, the thermal energy of the upstream side pipe can be conducted to the downstream side pipe through the bracket. In a case where the heat exchanger is configured to include two or more brackets, it is also possible to conduct more heat energy from the upstream side pipe to the downstream side pipe.

In a case where the heat exchanger is configured to include one or more brackets, one of the one or more brackets may be disposed close to the connection portion between the upstream side pipe and the exhaust pipe. Here, at the connection portion between the upstream side pipe and the exhaust pipe, the thermal energy is directly conducted from the exhaust pipe to the upstream side pipe. Therefore, the upstream side pipe near the connection portion has a relatively large amount of thermal energy. Therefore, when the bracket is disposed close to the connection portion, it is possible to conduct more thermal energy from the upstream side pipe to the downstream side pipe.

In a case where the heat exchanger is configured to include one or more brackets, at least one of the one or more brackets may be fixed to the exhaust pipe. In this case, the bracket can also conduct heat energy from the exhaust pipe to the downstream side pipe in addition to conducting heat energy from the upstream side pipe to the downstream side pipe. As a result, it is possible to more reliably increase the temperature of the downstream side pipe.

The configuration of the heat exchanger is not limited to the above-described configuration, and may include a cover that covers the upstream side pipe and the downstream side pipe together. In this case, the thermal energy dissipated from the upstream side pipe can be conducted to the downstream side pipe.

Embodiment

Hereinafter, specific embodiments of the present disclosure will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the disclosure to the dimensions, materials, shapes, relative arrangements, and the like unless otherwise specified.

Exhaust System Overview

In the present embodiment, an example in which the exhaust system according to the present disclosure is applied to an internal combustion engine for a vehicle will be described. The vehicle may be, for example, a vehicle (an internal combustion engine vehicle) driven by an internal combustion engine as a prime mover. The vehicle is not limited to an internal combustion engine vehicle. The vehicle may be a vehicle (hybrid electric vehicle (HEV) or plug-in hybrid electric vehicle (PHEV)) driven by an internal combustion engine and an electric motor as a prime mover. The vehicle may be a battery electric vehicle (BEV) that is equipped with an internal combustion engine as a generator.

FIG. 1 is a diagram schematically showing an example of a configuration of an exhaust system Es1 of an internal combustion engine 1 in the present embodiment. The internal combustion engine 1 may be a spark ignition type internal combustion engine (gasoline engine) having a plurality of cylinders 10 in one example. The exhaust system Es1 is configured to include an exhaust manifold 2, a catalyst casing 3, an exhaust pipe 4, a filter casing 5, and an insulator 6 in one example.

The exhaust manifold 2 is connected to the internal combustion engine 1 and is configured to allow the burnt gas combusted in the cylinders 10 of the internal combustion engine 1 to flow. In an example, the exhaust manifold 2 may be configured to include a plurality of branch pipes through which the burned gas (exhaust gas) burned in each of the cylinders 10 of the internal combustion engine 1 flows and a merged pipe (collector) that merges the exhaust gas flowing through the branch pipes.

The catalyst casing 3 is connected to a downstream side (a confluence pipe) of the exhaust manifold 2 and is configured to purify exhaust gas flowing out of the exhaust manifold 2. In an example, the catalyst casing 3 may be configured to house an exhaust gas cleaning catalyst, such as a three-way catalyst, in a cylindrical casing and clean exhaust components, such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO_x), contained in exhaust gas.

The exhaust pipe 4 is connected to a downstream side of the catalyst casing 3 and is configured to allow the exhaust gas flowing out of the catalyst casing 3 to flow. In an example, the exhaust pipe 4 may be formed of a cylindrical metal pipe.

The filter casing 5 is disposed in the middle of the exhaust pipe 4 and houses a gasoline particulate filter (GPF). The GPF is a filter for collecting particulate matter (PM) contained in exhaust gas.

The insulator 6 is a cover that covers the upper portion (the portion in the front direction in FIG. 1) of the exhaust manifold 2 and the catalyst casing 3, and is formed of a member having heat insulating properties. The insulator 6 may be configured to cover not only the upper portion of the exhaust manifold 2 and the catalyst casing 3 but also the entire upper, lower, left, and right portions of the exhaust manifold 2 and the catalyst casing 3. In addition, the insulator 6 may be configured to cover solely the exhaust manifold 2 among the exhaust manifold 2 and the catalyst casing 3.

In addition, the exhaust system Es1 in the present embodiment further includes a differential pressure sensor 7, an upstream side pipe 70, a downstream side pipe 71, and a heat exchanger 8. The differential pressure sensor 7 is a sensor used for calculating the amount of PM collected in the GPF in the filter casing 5, detecting the removal of the GPF, and the like, and detects a differential pressure between an exhaust pressure upstream of the GPF and an exhaust pressure downstream of the GPF. In the example shown in FIG. 1, the differential pressure sensor 7 is fixed to the internal combustion engine 1. The disposition of the differential pressure sensor 7 is not limited to the disposition illustrated in FIG. 1, and can be appropriately changed according to the aspect of the disclosure.

One end of an upstream side pipe 70 and one end of a downstream side pipe 71 are connected to the differential pressure sensor 7 of the present embodiment, respectively. The other end of the upstream side pipe 70 is connected to an exhaust pipe 4 upstream of the filter casing 5, and transmits an exhaust pressure upstream of the GPF to the differential pressure sensor 7. The other end of the downstream side pipe 71 is connected to an exhaust pipe 4 downstream of the filter casing 5, and transmits an exhaust pressure downstream of the GPF to the differential pressure sensor 7. In the present embodiment, as illustrated in FIG. 1, the upstream side pipe 70 and the downstream side pipe 71 are disposed above the insulator 6. The other end of the upstream side pipe 70 may be connected to the filter casing 5 upstream of the GPF. In addition, the other end of the downstream side pipe 71 may be connected to the filter casing 5 downstream of the GPF.

The heat exchanger 8 is a member for performing heat exchange between the upstream side pipe 70 and the downstream side pipe 71. The heat exchanger 8 is configured to perform positioning of the upstream side pipe 70 and the downstream side pipe 71. As a result, the upstream side pipe 70 and the downstream side pipe 71 are disposed in parallel to each other along the flow direction of the exhaust gas. Details of the heat exchanger 8 will be described below.

In the present embodiment, the combination of the exhaust manifold 2, the catalyst casing 3, and the exhaust pipe 4 corresponds to the exhaust pipe according to the present disclosure.

Configuration of Heat Exchanger

Here, an example of the configuration of the heat exchanger 8 in the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 2 is a cross-sectional view schematically showing an example of the configuration of the first bracket 80 included in the heat exchanger 8 in the present embodiment. FIG. 3 is a cross-sectional view schematically showing an example of the configuration of the second bracket 81 included in the heat exchanger 8 in the present embodiment. FIGS. 2 and 3 are cross-sectional views as seen from the differential pressure sensor 7 in the axial direction of the upstream side pipe 70 and the downstream side pipe 71 in the arrangement illustrated in FIG. 1.

The heat exchanger 8 in the present embodiment is configured to include a first bracket 80 and a second bracket 81 as shown in FIG. 1. The first bracket 80 and the second bracket 81 are formed of a material having high thermal conductivity (for example, a metal such as copper or aluminum). The first bracket 80 and the second bracket 81 are members for positioning the upstream side pipe 70 and the downstream side pipe 71. The upstream side pipe 70 and the downstream side pipe 71 are disposed in parallel to each other in the flow direction of the exhaust gas.

In the example shown in FIG. 1, the first bracket 80 is disposed at a position closer to the differential pressure sensor 7 than the second bracket 81. Specifically, the first bracket 80 is disposed on an upper surface of a portion of the insulator 6 that covers the exhaust manifold 2. The first bracket 80 according to the embodiment is configured to sandwich the upstream side pipe 70 and the downstream side pipe 71 in parallel and close to each other, as shown in FIG. 2, for example. Further, the first bracket 80 is tightened (fixed) together with the insulator 6 to the exhaust manifold 2 by the stud bolt 20 embedded in the exhaust manifold 2 and the nut 813 screwed to the stud bolt 20. In this case, the stud bolt 20 and the nut 813 may be formed of a material having a high thermal conductivity (for example, a metal such as copper or aluminum) in the same manner as the first bracket 80.

As illustrated in FIG. 1, the second bracket 81 is disposed at a position farther from the differential pressure sensor 7 than the first bracket 80. Specifically, the second bracket 81 is disposed close to a connection portion C1 (hereinafter, also referred to as “first connection portion C1”) between the upstream side pipe 70 and the exhaust pipe 4. The second bracket 81 may be configured to include, for example, a pair of holders 810, 811 that holds the upstream side pipe 70 and the downstream side pipe 71 in parallel and close to each other, as shown in FIG. 3. The holders 810, 811 may be fixed to each other by a bolt 812 and a nut 813. The configuration of the second bracket 81 is not limited to the example shown in FIG. 3, and may be a configuration in which the upstream side pipe 70 and the downstream side pipe 71 can be fixed in parallel and close to each other.

Action and Effect of Embodiment

In the exhaust system Es1 of the present embodiment, the thermal energy of the exhaust pipe 4 is transmitted to the upstream side pipe 70 through the first connection portion C1. In addition, the thermal energy of the exhaust pipe 4 is also transmitted to the downstream side pipe 71 through the connection portion C2 (hereinafter, also referred to as “second connection portion C2”) between the downstream side pipe 71 and the exhaust pipe 4.

Note that the second connection portion C2 is disposed at a position farther from the internal combustion engine 1 that is a heat source than the first connection portion C1. Therefore, the amount of heat energy transmitted from the exhaust pipe 4 to the downstream side pipe 71 through the second connection portion C2 is likely to be smaller than the amount of heat energy transmitted from the exhaust pipe 4 to the upstream side pipe 70 through the first connection portion C1. In addition, since the length of the downstream side pipe 71 is longer than the length of the upstream side pipe 70, the amount of thermal energy (heat dissipation amount) dissipated from the downstream side pipe 71 to the atmosphere tends to be larger than the heat dissipation amount from the upstream side pipe 70.

On the other hand, in the exhaust system Es1 of the present embodiment, the upstream side pipe 70 and the downstream side pipe 71 are connected through the first bracket 80 and the second bracket 81. Therefore, the thermal energy of the upstream side pipe 70 is transmitted to the downstream side pipe 71 through the first bracket 80 and the second bracket 81. In addition, the first bracket 80 of the present embodiment is connected to the exhaust manifold 2 via the stud bolt 20 and the nut 21. Therefore, the thermal energy of the exhaust manifold 2 is transmitted to the upstream side pipe 70 and the downstream side pipe 71 through the first bracket 80. Further, since the second bracket 81 of the present embodiment is disposed close to the first connection portion C1, the thermal energy transmitted from the exhaust pipe 4 to the upstream side pipe 70 through the first connection portion C1 is also transmitted to the downstream side pipe 71 through the second bracket 81.

Therefore, with the exhaust system Es1 of the present embodiment, the temperature of the downstream side pipe 71 can be increased in a case where the vehicle is used in an environment in which the outside air temperature is at or below the freezing point, such as a cold region. As a result, it is possible to suppress the freezing of the condensed water inside the downstream side pipe 71. Further, even in a case where the condensed water is frozen inside the downstream side pipe 71 while the internal combustion engine 1 is stopped, it is also possible to quickly thaw the condensed water inside the downstream side pipe 71 after the internal combustion engine 1 is started. Therefore, it is possible to more reliably suppress the blockage of the inside of the downstream side pipe 71 with the condensed water due to freezing. As a result, it is possible to suppress a decrease in the accuracy of the differential pressure sensor 7.

Others

In the above-described embodiment, a spark ignition type internal combustion engine (gasoline engine) has been described as an example of the internal combustion engine to which the exhaust system according to the present disclosure is applied, but a compression ignition type internal combustion engine (diesel engine) may be used. In this case, a DPF (diesel particulate filter) may be housed in the filter casing 5 instead of the GPF. In the embodiment described above, the configuration in which the catalyst casing 3 is disposed upstream of the filter casing 5 has been described as an example, but the catalyst casing 3 may be omitted. In this case, the exhaust gas cleaning catalyst may be supported on the GPF.